Many non-steroid anti-inflammatory products have been discovered in the last twenty years. However, the search continues for compounds that are more effective and better tolerated in comparison with present products and their development remains a major objective of therapeutic research.
A. Ermili and L. Salamon have described some 5,6-dihydro-6-alkyl-2-aryl-4H-cyclopenta[b]thiophene-5-carboxylic acids and 5,6-dihydro-6-alkyl-2-aryl-4H-cyclopenta[b]thiophene-4-carboxylic acids [Ann. Chim. (Rome) 1969, 59, 375]. German patent No. 2,443,086 has as its object 2-aryl-3-hydroxy or alkoxy-5,6-dihydro-4H-cyclopenta[b]thiophene-4-carboxylic acids. Mention is made in Spanish Pat. No. 468,064 of 5,6-dihydro-4H-cyclopenta[b]thiophene-4-carboxylic acid. 5,6-Dihydro-4H-cyclopenta[b]thiophene-4-carboxylic acids able to carry a benzoyl group in the 2 or 3 position were presented as anti-inflammatory agents in Spanish Pat. No. 487,841, the preferred product being 2-isobutyl-5,6-dihydro-4H-cyclopenta[b]thiophene-4-carboxylic acid. Finally, the preparation of 5-ethyl-5,6-dihydro-4H-cyclopenta[b]thiophene-6-carboxylic acid appears in Spanish Pat. No. 468,129.